thr3ads.net - llvm dev - [llvm-dev] Question on target-features [Sep 2019]

If this information is useful, please help other people find it:
Share via:

Krzysztof Parzyszek via llvm-dev

2019-Sep-27 15:07 UTC

[llvm-dev] Question on target-features

Ugh, that would be a “yes” then…

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Krzysztof
Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 10:05 AM
To: Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>; llvm-dev at
lists.llvm.org
Subject: [EXT] Re: [llvm-dev] Question on target-features

No.  The way +feature works is that it causes the assignment Attribute=Value to
happen, where Attribute and Value are strings defined in a td file.  With
-feature, this assignment does not happen, so whatever the default value is of
Attribute, it will remain unchanged.

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces
at lists.llvm.org>> On Behalf Of Dangeti Tharun kumar via llvm-dev
Sent: Friday, September 27, 2019 9:23 AM
To: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at
lists.llvm.org>>
Subject: [EXT] [llvm-dev] Question on target-features

Hi,

In "target-features" list in LLVM-IR, there are "+feature",
"-feature". My question is, does "-feature" is equivalent to
not specifying a feature at all?
For example:
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx -avx2" }
Wheather it is equalent to omitting the avx2 from list?
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx" }
--
Regards,
DTharun
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20190927/c4fed4af/attachment.html>

Cranmer, Joshua via llvm-dev

2019-Sep-27 15:11 UTC

head link

[llvm-dev] Question on target-features

Since the target cpu is znver2, which has avx2, target-features of “+avx -avx2”
is not equivalent to “+avx”. So the two attributes in the original question are
not equivalent.

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Krzysztof
Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 11:07
To: Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>; llvm-dev at
lists.llvm.org
Subject: Re: [llvm-dev] Question on target-features

Ugh, that would be a “yes” then…

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces
at lists.llvm.org>> On Behalf Of Krzysztof Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 10:05 AM
To: Dangeti Tharun kumar <cs15mtech11002 at
iith.ac.in<mailto:cs15mtech11002 at iith.ac.in>>; llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: [EXT] Re: [llvm-dev] Question on target-features

No.  The way +feature works is that it causes the assignment Attribute=Value to
happen, where Attribute and Value are strings defined in a td file.  With
-feature, this assignment does not happen, so whatever the default value is of
Attribute, it will remain unchanged.

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces
at lists.llvm.org>> On Behalf Of Dangeti Tharun kumar via llvm-dev
Sent: Friday, September 27, 2019 9:23 AM
To: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at
lists.llvm.org>>
Subject: [EXT] [llvm-dev] Question on target-features

Hi,

In "target-features" list in LLVM-IR, there are "+feature",
"-feature". My question is, does "-feature" is equivalent to
not specifying a feature at all?
For example:
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx -avx2" }
Wheather it is equalent to omitting the avx2 from list?
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx" }
--
Regards,
DTharun
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20190927/3ca27129/attachment.html>

Krzysztof Parzyszek via llvm-dev

2019-Sep-27 15:13 UTC

head link

[llvm-dev] Question on target-features

This thread is getting from bad to worse…  Certain features are assumed as
default for a given processor, so -feature will actually have an effect of
removing it from the feature string that is parsed in the subtarget.  Back to
“no”…

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Krzysztof
Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 10:07 AM
To: Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>; llvm-dev at
lists.llvm.org
Subject: [EXT] Re: [llvm-dev] Question on target-features

Ugh, that would be a “yes” then…

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces
at lists.llvm.org>> On Behalf Of Krzysztof Parzyszek via llvm-dev
Sent: Friday, September 27, 2019 10:05 AM
To: Dangeti Tharun kumar <cs15mtech11002 at
iith.ac.in<mailto:cs15mtech11002 at iith.ac.in>>; llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: [EXT] Re: [llvm-dev] Question on target-features

No.  The way +feature works is that it causes the assignment Attribute=Value to
happen, where Attribute and Value are strings defined in a td file.  With
-feature, this assignment does not happen, so whatever the default value is of
Attribute, it will remain unchanged.

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   AI tools development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces
at lists.llvm.org>> On Behalf Of Dangeti Tharun kumar via llvm-dev
Sent: Friday, September 27, 2019 9:23 AM
To: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at
lists.llvm.org>>
Subject: [EXT] [llvm-dev] Question on target-features

Hi,

In "target-features" list in LLVM-IR, there are "+feature",
"-feature". My question is, does "-feature" is equivalent to
not specifying a feature at all?
For example:
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx -avx2" }
Wheather it is equalent to omitting the avx2 from list?
attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx" }
--
Regards,
DTharun
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20190927/396eba12/attachment.html>

Craig Topper via llvm-dev

2019-Sep-27 16:02 UTC

head link

[llvm-dev] Question on target-features

And -feature will remove all other features that depend on the feature. So
for x86, -sse2 will disable sse2, sse3, sse4.1, sse4.2, avx, avx2, etc.

On Fri, Sep 27, 2019 at 8:13 AM Krzysztof Parzyszek via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> This thread is getting from bad to worse…  Certain features are assumed as
> default for a given processor, so -feature will actually have an effect of
> removing it from the feature string that is parsed in the subtarget.  Back
> to “no”…
>
>
>
> --
>
> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*Krzysztof
> Parzyszek via llvm-dev
> *Sent:* Friday, September 27, 2019 10:07 AM
> *To:* Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>;
> llvm-dev at lists.llvm.org
> *Subject:* [EXT] Re: [llvm-dev] Question on target-features
>
>
>
> Ugh, that would be a “yes” then…
>
>
>
> --
>
> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*Krzysztof
> Parzyszek via llvm-dev
> *Sent:* Friday, September 27, 2019 10:05 AM
> *To:* Dangeti Tharun kumar <cs15mtech11002 at iith.ac.in>;
> llvm-dev at lists.llvm.org
> *Subject:* [EXT] Re: [llvm-dev] Question on target-features
>
>
>
> No.  The way +feature works is that it causes the assignment
> Attribute=Value to happen, where Attribute and Value are strings defined in
> a td file.  With -feature, this assignment does not happen, so whatever the
> default value is of Attribute, it will remain unchanged.
>
>
>
> --
>
> Krzysztof Parzyszek  kparzysz at quicinc.com   AI tools development
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*Dangeti
> Tharun kumar via llvm-dev
> *Sent:* Friday, September 27, 2019 9:23 AM
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [EXT] [llvm-dev] Question on target-features
>
>
>
> Hi,
>
>
>
> In "target-features" list in LLVM-IR, there are
"+feature", "-feature". My
> question is, does "-feature" is equivalent to not specifying a
feature at
> all?
>
> For example:
>
> *attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx
> -avx2" }*
>
> Wheather it is equalent to omitting the avx2 from list?
>
> *attributes #0 = {  "target-cpu"="znver2" 
"target-features"="+avx" }*
>
> --
>
> Regards,
>
> DTharun
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>-- 
~Craig
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20190927/15f9c176/attachment.html>

llvm dev - Sep 2019 - Question on target-features

[llvm-dev] Question on target-features

[llvm-dev] Question on target-features

[llvm-dev] Question on target-features

[llvm-dev] Question on target-features